A warrior of the Kajiwara branch of the Kanmu Heishi Kamakura clan, based in Sagami Province (modern Kamakura). In 1180, when Minamoto no Yoritomo first raised his banner, Kagetoki initially fought against him under Oba Kagechika at the Battle of Ishibashiyama — but spared the hiding Yoritomo, an act later called 'Kajiwara's Pardon' that secured the foundation of the Kamakura shogunate. He soon joined Yoritomo and rose rapidly thanks to his literary education and administrative talent, serving as deputy head of the Samurai-dokoro (military office) and as shugo of Harima and Mimasaka provinces. He served as military aide-de-camp to Yoshitsune at Ichi-no-Tani (1184) and Dan-no-ura (1185), but their bitter dispute over the 'reverse oars' tactic at Yashima and his subsequent slanders against Yoshitsune earned him posthumous notoriety as the 'instigator of Yoshitsune's downfall.' After Yoritomo's sudden death in 1199, his accusation against the vassal Yuki Tomomitsu provoked 66 leading vassals — led by Miura Yoshizumi and Wada Yoshimori — to submit a petition demanding his expulsion. Driven from Kamakura, he was killed in January 1200 at Kiyomi-ga-seki in Suruga Province (modern Shimizu, Shizuoka) together with his eldest son Kageu and 23 clan members, becoming the first of the 'Thirteen Lords' to be eliminated. Played by Nakamura Shido II in the 2022 NHK taiga drama, his complex legacy has been widely re-examined.

A rare blend of warrior and scholar, equally at home with classical Chinese learning and waka poetry — known as the "singing samurai." Yoritomo trusted him absolutely, yet his readiness to denounce rivals earned him fear among other vassals as "the very embodiment of the Kamakura warrior." A man of fastidious principle whose loyalty to the institution sometimes overrode his loyalty to comrades, as exemplified by his feud with Yoshitsune.

His sparing of Yoritomo at Ishibashiyama is remembered as a historical turning point. As Yoritomo's confidant he helped establish the Samurai-dokoro institution. Long maligned as the "treacherous slanderer of Yoshitsune," he is now being reappraised as a victim of post-mortem character assassination in the Azuma Kagami compiled under Hojo influence. His former residence in Kamakura and burial site in Suruga remain as historical landmarks.